This invention relates to devices for treatment of heart diseases and more particularly, to a retractable sleeve for use in a stent delivery system.
Several interventional treatment modalities are presently used for heart disease including balloon and laser angioplasty, atherectomy and by-pass surgery. In typical balloon angioplasty procedures, a guiding catheter having a preformed distal tip is percutaneously introduced through the femoral artery into the cardiovascular system of a patient in a conventional Seldinger technique and advanced within the cardiovascular system until the distal tip of the guiding catheter is seated in the ostium of a desired coronary artery. A guidewire is positioned within an inner lumen of a dilatation catheter and then both are advanced through the guiding catheter to the distal end thereof. The guidewire is first advanced out the distal end of the guiding catheter into the coronary vasculature until the distal end of the guidewire crosses a lesion to be dilated, then the dilatation catheter having an inflatable balloon on the distal portion thereof is advanced into the patient's coronary anatomy over the previously introduced guidewire until the balloon the dilatation catheter are properly positioned across the lesion.
Once in position across the lesion, the balloon, which is made of relatively inelastic materials, is inflated to predetermined size with radiopaque liquid at a relatively high pressure (e.g., greater than four atmospheres) to compress the arteriosclerotic plaque of the lesion against the inside of the arterial wall and to otherwise expand the inner lumen of the artery. The balloon is then deflated so that the blood flow can be resumed through the dilatated artery and the dilatation catheter can be removed therefrom. Further details of dilatation catheters, guidewires, and devices associated therewith for angioplasty procedures can be found in Simpson, et al. U.S. Pat. No. 4,323,071; Sampson, et al. U.S. Pat. No. 4,554,929; Simpson U.S. Pat. No. 4,616,652; Powell U.S. Pat. No. 4,638,805; and Horzewski, et al. U.S. Pat. No. 4,748,982, which are incorporated herein in their entirety by reference thereto.
A major focus of recent development work in the treatment of heart disease has been directed to endoprosthetic devices called stents. Stents are generally cylindrically-shaped intravascular devices which are placed within a damaged artery to hold it open. The device can be used to prevent restenosis and to maintain the patency of a blood vessel immediately after intravascular treatments. In some circumstances, they can also be used as the primary treatment device where they are expanded to dilate a stenosis and then left in place.
The rapid and effective delivery of a stent to a designated location within the patient's vasculature is desirable, particularly where the stent is to be delivered within a coronary artery. That is, quickly placing a stent within a patient's vasculature is desirable since the intrusive nature of the angioplasty procedure and the associated danger to the patient may then be minimized. It has been found to be difficult to quickly deliver a stent, however, particularly in those situations in which an intimal flap has occluded an artery.
Attempts to advance and place a stent in regions of coronary arteries occluded by dissected arterial linings have had varying degrees of success. A successful method for rapidly and effectively delivering a stent involves placing a compressed or otherwise small diameter stent about an expandable member, such as a balloon, on the distal end of an intravascular catheter and slidably disposing the intravascular catheter within an elongated sheath having a distal port through which the catheter may egress. Thereafter, the sheath and catheter may be advanced through the patient's vascular system until they are in the desired location within a blood vessel and the relative axial positions of the sheath and catheter may be manipulated so that the entire length of the stent mounted on the distal extremity of the catheter is emitted from the sheath. Next, the balloon catheter may be expanded so as to seat the stent within the blood vessel. Finally, the balloon catheter is deflated and the sheath and catheter are withdrawn, leaving the expanded stent within the blood vessel holding open the passageway thereof.
However, during the advancement through arduous turns of a patient's vasculature, the sheath and catheter of stent delivery systems heretofore provided may kink and buckle. The elongated portions of conventional systems may comprise homogeneous material selected to optimize longitudinal stiffness and lateral flexibility. In the selection of materials, however, it is necessary to compromise on stiffness or flexibility since homogeneous materials generally do not possess both and therefore, result in comprising structure that kinks and buckles. Kinking or buckling of stent delivery system structure may impede advancement thereof through a patient's vasculature or otherwise result in a damaged stent delivery system, necessitating removing the damaged system and repeating the procedure with a replacement system. Further, the patient's vasculature may be traumatized when a stent delivery catheter kinks and cannot be advanced in a tight turn. Since it is advantageous to quickly deliver a stent to a repair site within a patient's vasculature, a stent delivery system having improved stiffness, pushability and flexibility is desirable.
Accordingly, what is needed and heretofore unavailable is a stent delivery system comprising structure that avoids kinking and buckling while being advanced through a patient's vasculature. The present invention satisfies this need.